Telecommunication networks include circuit-switched networks such as plain old telephone service (POTS) and packet-switched networks such as the Internet Protocol (IP) network to transport voice and data between remote end users. The circuit-switched networks utilize transmission paths dedicated to specific users for the duration of a call and employ continuous, fixed bandwidth transmission. The packet-switched networks allow dynamic bandwidth, and can be connectionless networks with no dedicated circuit or connection-oriented networks with virtual circuits having dedicated bandwidth along a predetermined path. Because packet-switched networks allow traffic from multiple users to share communication links, these networks use available bandwidth more efficiently than circuit-switched networks.
IP networks are connectionless packet-switched networks that format streams of information into addressable packets. Each IP packet includes source and destination addresses and can take any available route between the source and destination. The IP packets are transmitted independently and then reassembled in the proper sequence at the destination.
Telephone calls and other voice traffic may be transmitted in an IP network using voice over IP (VoIP). In a VoIP environment, music-on-hold is implemented using music-on-hold servers that unicast or multicast music-on-hold streams. For better network utilization, multicast is usually preferred. Multicast streams are played out to endpoints or to trunking endpoints, which then transmit music to other endpoints that are placed on-hold. Typically, a call manager identifies predefined music-on-hold streams and/or servers for use by endpoints and takes action in case the identified music-on-hold servers fail. In a peer-to-peer communication environment, the music-on-hold servers are accessed without the control of a central call manager.